The present invention relates to a waveform data looping system for use in an electronic musical instrument to obtain a smooth change of waveform.
While playing an electronic musical instrument such as an electronic piano, there may be a demand for repeatedly listening to a portion of varying sound. In such a case, it has been routine to magnetically record that sound portion, to sample a waveform of the sound at a predetermined sampling time interval from an initial time to an end time of the sound portion, A/D convert the sampled values and to store them in a memory device as digital signals. Then, the stored signals are read out, D/A converted and reproduced, sequentially, and this operation is repeated. This repeated reproduction of such a portion of sound is referred to as "looping".
In the looping operation, the reproducing operation is returned from the end point of the sound to the start point repeatedly. In such a case, since the data value at the start point has no relation to that at the end point, there may be noise produced at a start of a new reproduction cycle. Further, since a tendency of change of a data value in a time period up to the end time point differs from that immediately after a new cycle starts, there may be discontinuity in volume and tone at such a change point of the reproduction cycle, which makes a listener uncomfortable.